Md-Vpn Overview - HP A8800 Configuration Manual

MD-VPN overview

NOTE:
For more information about the concepts of Protocol Independent Multicast (PIM), bootstrap router (BSR),
candidate-BSR (C-BSR), rendezvous point (RP), designated forwarder (DF), candidate-RP (C-RP), shortest
path tree (SPT) and rendezvous point tree (RPT), see
Basic concepts in MD-VPN
Concept
Multicast domain (MD)
Multicast distribution tree (MDT)
Multicast tunnel (MT)
Multicast tunnel interface (MTI)
Share-group
Share-multicast distribution tree
(Share-MDT)
Switch-multicast distribution tree
(Switch-MDT)
Switch-group
Switch-group-pool
"Configuring
Description
An MD is a set of VPN instances running on PE devices that can send
multicast traffic to each other. Each MD uniquely corresponds to the
same set of VPN instances.
An MDT is a multicast distribution tree between all PE devices in the
same VPN. There are two kinds of MDTs: share-MDT and switch-MDT.
An MT is a tunnel that interconnects all PEs in an MD for delivering VPN
traffic within the MD.
An MTI is the entrance to or exit of an MT, equivalent to an entrance to
or exit of an MD. PE devices use the MTI to access the MD. An MTI
handles only multicast packets but not unicast packets. An MTI is
automatically created with the configuration of a share-group and MTI
binding for a VPN instance.
In the public network, each MD is assigned an independent multicast
address, called share-group. A share-group is the unique identifier of
an MD on the public network. It is used to build a share-MDT
corresponding to the MD on the public network.
A share-MDT is an MDT that uses a share-group as its group address. In
a VPN, the share-MDT is uniquely identified by the share-group. A
share-MDT is automatically created after configuration and will always
exist on the public network, regardless of the presence of any actual
multicast services on the public network or the VPN.
A switch-MDT is an MDT that uses a switch-group as it group address.
At MDT switchover, PE devices with receivers downstream join a
switch-group, forming a switch-MDT, along which the ingress PE
forwards the encapsulated VPN multicast traffic over the public
network.
When the multicast traffic of a VPN reaches or exceeds a threshold, the
ingress PE device assigns it an independent multicast address called
switch-group, and notifies the other PE devices that they should use that
address to forward the multicast traffic for that VPN. This initiates a
switchover to the switch-MDT.
The switch-group-pool is a range of multicast addresses. At MDT
switchover, an address (namely, switch-group address) is chosen from
the switch-group-pool. The multicast packets for the VPN that enter the
public network at the PE device are to be encapsulated using that
address. The switch-group-pool of a VPN must not overlap that of
another VPN, and must not contain the share-group of another VPN.
242
PIM."